Of course, as Chas has said, it is your body, but if your goal is to be in keeping with the wishes of the traditional governing bodies, then it seems you may want to stick with this:

"Crest Badges are for wear by the clansmen, and as they are made of silver or white metal they should never be illustrated on paper or other materials in colour, other than white or silver. Line drawings should be printed in
monochrome."

In this instance, I would consider a tattoo a line drawing. And as you have no control over your skin color, would do a line drawing in some variant of the most common color of line drawings, black.

If, again assuming you are wanting to "follow the rules" so to speak, you wish to do something in color, Chas' directions would indicate that a request to your clan chief would be in order to receive his blessings (or not).

That, of course, is just my take on the information you and Chas have provided. Others, with far greater knowledge than me, may suggest otherwise.

Good luck!